[PATCH v3 20/46] perf/core: add pmu::event_terminate

[David Carrillo-Cisneros]

The new pmu::event_terminate allows a PMU to access an event's cgroup
before the event is torn down.

Used in CMT to dettach the cgroup from a monr before perf clears
event->cgrp.

Signed-off-by: David Carrillo-Cisneros <davidcc@xxxxxxxxxx>
---
 include/linux/perf_event.h | 6 ++++++
 kernel/events/core.c       | 4 ++++
 2 files changed, 10 insertions(+)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 406119b..14dff7a 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -298,6 +298,12 @@ struct pmu {
 	int (*event_init)		(struct perf_event *event);
 
 	/*
+	 * Terminate the event for this PMU. Optional complement for a
+	 * successful event_init. Called before the event fields are tear down.
+	 */
+	void (*event_terminate)		(struct perf_event *event);
+
+	/*
 	 * Notification that the event was mapped or unmapped.  Called
 	 * in the context of the mapping task.
 	 */
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 0de3ca5..464f46d 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4005,6 +4005,8 @@ static void _free_event(struct perf_event *event)
 		ring_buffer_attach(event, NULL);
 		mutex_unlock(&event->mmap_mutex);
 	}
+	if (event->pmu->event_terminate)
+		event->pmu->event_terminate(event);
 
 	if (is_cgroup_event(event))
 		perf_detach_cgroup(event);
@@ -9226,6 +9228,8 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 	exclusive_event_destroy(event);
 
 err_pmu:
+	if (event->pmu->event_terminate)
+		event->pmu->event_terminate(event);
 	if (event->destroy)
 		event->destroy(event);
 	module_put(pmu->module);
-- 
2.8.0.rc3.226.g39d4020